Effects of dense planting patterns on photosynthetic traits of different vertical layers and yield of wheat under different nitrogen rates

A two-year field experiment was conducted to measure the effects of densification methods on photosynthesis and yield of densely planted wheat.Inter-plant and inter-row distances were used to define ratefixed pattern(RR)and row-fixed pattern(RS)density treatments.Meanwhile,four nitrogen(N)rates(0,144,192,and 240 kg N ha-1,termed N0,N144,N192,and N240)were applied with three densities(225,292.5,and 360×10^(4)plants ha^(-1),termed D225,D292.5,and D360).The wheat canopy was clipped into three equal vertical layers(top,middle,and bottom layers),and their chlorophyll density(Ch D)and photosynthetically active radiation interception(FIPAR)were measured.Results showed that the response of Ch D and FIPAR to N rate,density,and pattern varied with different layers.N rate,density,and pattern had significant interaction effects on Ch D.The maximum values of whole-canopy Ch D in the two seasons appeared in N240 combined with D292.5 and D360 under RR,respectively.Across two growing seasons,FIPAR values of RR were higher than those of RS by 29.37%for the top layer and 5.68%for the middle layer,while lower than those of RS by 20.62%for the bottom layer on average.With a low N supply(N0),grain yield was not significantly affected by density for both patterns.At N240,increasing density significantly increased yield under RR,but D360 of RS significantly decreased yield by 3.72%and 9.00%versus D225 in two seasons,respectively.With an appropriate and sufficient N application,RR increased the yield of densely planted wheat more than RS.Additionally,the maximum yield in two seasons appeared in the combination of D360 with N144 or N192 rather than of D225 with N240 under both patterns,suggesting that dense planting combined with an appropriate N-reduction application is feasible to increase photosynthesis capacity and yield.

Melatonin delays leaf senescence in pak choi(Brassica rapa subsp.chinensis)by regulating biosynthesis of the second messenger cGMP

Melatonin(MT)is a low molecular weight compound with multiple biological functions in plants.It is known to delay leaf senescence in various species.However,no data are available on the MT signaling pathway in postharvest vegetables.This study demonstrates that MT increases cGMP concentration and the expression of the cGMP synthesis gene BcGC1 in pak choi.The c GMP inhibitor LY83583 destroys effect of MT delaying the leaf senescence.LY83583 also prevents MT treatment from reducing the expression of chlorophyll metabolism-related genes(BcNYC1,BcNOL,BcPPH1/2,BcSGR1/2,and BcPAO)and senescence genes(BcSAG12 and BcSAG21).It also inhibits MT from reducing the activity of the key chlorophyll catabolism enzymes Mg-dechelatase,pheophytinase,and pheide a oxygenase.Thus,the ability of MT to maintain high levels of chlorophyll metabolites is also destroyed.The Arabidopsis c GMP synthetic gene mutant atgc1 was used to confirm that delayed leaf senescence caused by MT is mediated,at least in part,by the second messenger c GMP.

Spatio-temporal variability of surface chlorophyll a in the Yellow Sea and the East China Sea based on reconstructions of satellite data of 2001-2020

Chlorophyll-a(Chl-a)concentration is a primary indicator for marine environmental monitoring.The spatio-temporal variations of sea surface Chl-a concentration in the Yellow Sea(YS)and the East China Sea(ECS)in 2001-2020 were investigated by reconstructing the MODIS Level 3 products with the data interpolation empirical orthogonal function(DINEOF)method.The reconstructed results by interpolating the combined MODIS daily+8-day datasets were found better than those merely by interpolating daily or 8-day data.Chl-a concentration in the YS and the ECS reached its maximum in spring,with blooms occurring,decreased in summer and autumn,and increased in late autumn and early winter.By performing empirical orthogonal function(EOF)decomposition of the reconstructed data fields and correlation analysis with several potential environmental factors,we found that the sea surface temperature(SST)plays a significant role in the seasonal variation of Chl a,especially during spring and summer.The increase of SST in spring and the upper-layer nutrients mixed up during the last winter might favor the occurrence of spring blooms.The high sea surface temperature(SST)throughout the summer would strengthen the vertical stratification and prevent nutrients supply from deep water,resulting in low surface Chl-a concentrations.The sea surface Chl-a concentration in the YS was found decreased significantly from 2012 to 2020,which was possibly related to the Pacific Decadal Oscillation(PDO).

Study on the Photosynthetic Characteristics of Six Varieties(Strains)in Chinese Chestnut

[Objectives]This study was conducted to investigate the differences of photosynthetic physiological characteristics of different varieties(strains),which will provide a theoretical basis for high photosynthesis efficiency breeding and application in Chinese chestnut.[Methods]Six Chinese chestnut varieties of Castanea mollissima‘Yanbao’,C.mollissima‘Yanqiu’,C.mollissima‘Yanchang’,C.mollissima‘Yanjia’,C.mollissima‘Qianxi 37’,and C.mollissima‘Hybrid 22’were used as the materials.Using the portable photosynthesis system Li-6400,we measured the photosynthetic characteristics and diurnal variation of leaf samples of six different chestnut varieties or strains.We fitted the light response curves and photosynthetic parameters using the leaf floating model.Additionally,we determined the chlorophyll content in the leaves using a UV-visible spectrophotometer.[Results]Among the six chestnut varieties or strains,‘Yanqiu’exhibited a significantly higher photosynthetic light saturation point(P LSP)compared to other five varieties,and‘Hybrid 22’ranked second,indicating that these two varieties had the strongest adaptation to high light intensity.The photosynthetic light compensation point(P LCP)of‘Yanchang’was significantly higher than other five varieties,and"Qianxi 37"ranked second,indicating that these two varieties had the strongest adaptation to low light intensity.Additionally,they exhibited higher chlorophyll content and maintained good photosynthetic characteristics even in shaded environments with weak light stress.Varieties‘Yanbao’and‘Yanjia’showed higher P LSP and lower P LCP,indicating that these two varieties have a wider range of adaptation to light intensity.They were capable of efficiently utilizing light across a broader spectrum of intensities.‘Yanqiu’had the highest maximum net photosynthetic rate(P n,max)and the lowest dark respiration rate(R d),along with the highest chlorophyll content.It indicated that‘Yanqiu’has strong photosynthetic capacity and organic matter accumulation ability.It also had the highest P LSP,enabling it to fully utilize the high light environment of the Yanshan Mountains and possessed high light efficiency characteristics.The P n,max of‘Yanqiu’was significantly higher than other varieties.‘Hybrid 22’and‘Yanbao’also exhibited significantly higher P n,max compared with‘Yanjia’and‘Qianxi 37’.‘Yanchang’had the lowest P n,max.The order of P n,max among the six chestnut varieties or strains was as follows:‘Yanqiu’>‘Hybrid 22’>‘Yanbao’>‘Yanjia’>‘Qianxi 37’>‘Yanchang’.[Conclusions]

GOLDEN 2-LIKE transcription factors regulate chlorophyll biosynthesis and flavonoid accumulation in response to UV-B in tea plants

Flavonoids are critical secondary metabolites that determine the health benefits and flavor of tea,while chlorophylls are important contributors to the appearance of tea.However,transcription factors(TFs)that can integrate both chlorophyll biosynthesis and flavonoid accumulation in response to specific light signals are rarely identified.In this study,we report that the GOLDEN 2-LIKE TF pair,CsGLK1 and CsGLK2,orchestrate UV-B-induced responses in the chlorophyll biosynthesis and flavonoid accumulation of tea leaves.The absence of solar UV-B reduced the transcriptional expression of CsGLKs in the tea leaves and was highly correlated with a decrease in flavonoid levels(especially flavonol glycosides)and the expression of genes and TFs involved in chlorophyll biosynthesis and flavonoid accumulation.In vivo and in vitro molecular analyses showed that CsGLKs could be regulated by the UV-B signal mediator CsHY5,and could directly bind to the promoters of gene and TF involved in light-harvesting(CsLhcb),chlorophyll biosynthesis(CsCHLH,CsHEMA1,and CsPORA),and flavonoid accumulation(CsMYB12,CsFLSa,CsDFRa,and CsLARa),eventually leading to UV-B-induced responses in the chlorophylls and flavonoids of tea leaves.Furthermore,UV-B exposure increased the levels of total flavonoids,CsGLK1 protein,and expression of CsGLKs and target genes in the tea leaves.These results indicate that CsGLKs may modulate tea leaf characteristics by regulating chlorophyll biosynthesis and flavonoid accumulation in response to solar UV-B.As the first report on UV-B-induced changes in flavonoid and chlorophyll regulation mediated by CsGLKs,this study improves our understanding of the environmental regulations regarding tea quality and sheds new light on UV-B-induced flavonoid responses in higher plants.

A novel single-base mutation in CaSGR1 confers the stay-green phenotype in pepper

The stay-green trait is of considerable importance in extending the shelf life of green pepper fruit(Capsicum annuum L.)and in enhancing the appearance of ornamental plants.The study revealed the genetic and regulatory mechanisms of the stay-green trait in pepper,which will aid in the selection of ornamental pepper varieties.In this study,a pepper mutant with stay-green fruit named TNX348 was identified from a germplasm resource bank.Two segregating populations were constructed using the stay-green mutant TNX348 and then used in bulked segregant analysis combined with RNA sequencing and linkage analyses.The causal gene of the stay-green trait was mapped to an approximately 131-kb region,and a senescence-induced chloroplast protein gene,CaSGR1(Capana01g000359),was identified as a candidate gene.Sequencing analysis revealed a G→A single-base mutation of CaSGR1 in TNX348 that led to early termination of translation.Based on the single-base mutation,a single nucleotide polymorphism(SNP)marker co-segregating with the stay-green trait was developed.Furthermore,in transcriptome analysis,expression patterns of 11 hormone transduction-related transcription factors,such as abscisic acid-insensitive(ABI),abscisic acidresponsive element-binding factor(ABF),and NAC transcription factor,were similar or opposite to that of CaSGR1.The results indicated that the transcription factors might mediate chlorophyll degradation by regulating the expression of CaSGR1.

Retrieving chlorophyll content and equivalent water thickness of Moso bamboo(Phyllostachys pubescens) forests under Pantana phyllostachysae Chao-induced stress from Sentinel-2A/B images in a multiple LUTs-based PROSAIL framework

Biochemical components of Moso bamboo(Phyllostachys pubescens)are critical to physiological and ecological processes and play an important role in the material and energy cycles of the ecosystem.The coupled PROSPECT with SAIL(PROSAIL)radiative transfer model is widely used for vegetation biochemical component content inversion.However,the presence of leaf-eating pests,such as Pantana phyllostachysae Chao(PPC),weakens the performance of the model for estimating biochemical components of Moso bamboo and thus must be considered.Therefore,this study considered pest-induced stress signals associated with Sentinel-2A/B images and field data and established multiple sets of biochemical canopy reflectance look-up tables(LUTs)based on the PROSAIL framework by setting different parameter ranges according to infestation levels.Quantitative inversions of leaf area index(LAI),leaf chlorophyll content(LCC),and leaf equivalent water thickness(LEWT)were derived.The scale conversions from LCC to canopy chlorophyll content(CCC)and LEWT to canopy equivalent water thickness(CEWT)were calculated.The results showed that LAI,CCC,and CEWT were inversely related with PPC-induced stress.When applying multiple LUTs,the p-values were<0.01;the R2 values for LAI,CCC,and CEWT were 0.71,0.68,and 0.65 with root mean square error(RMSE)(normalized RMSE,NRMSE)values of 0.38(0.16),17.56μg cm-2(0.20),and 0.02 cm(0.51),respectively.Compared to the values obtained for the traditional PROSAIL model,for October,R2 values increased by 0.05 and 0.10 and NRMSE decreased by 0.09 and 0.02 for CCC and CEWT,respectively and RMSE decreased by 0.35μg cm-2 for CCC.The feasibility of the inverse strategy for integrating pest-induced stress factors into the PROSAIL model,while establishing multiple LUTs under different pest-induced damage levels,was successfully demonstrated and can potentially enhance future vegetation parameter inversion and monitoring of bamboo forest health and ecosystems.

Analysis of Seasonal Differences of Chlorophyll,Dimethylsulfide,and Ice Between the Greenland Sea and the Barents Sea

Arctic Ocean(AO)climate is closely related to sea ice concentration(ICE)and chlorophyll_a(CHL)concentrations.From 2003–2014,the spatial average concentrations of CHL,ICE,sea surface temperature(SST),wind speed(WIND)in the Greenland Sea region(GS)(20˚W–10˚E,70˚–80˚N)and the Barents Sea region(BS)(30˚–50˚E,70˚–80˚N)are analysed and com-pared.Higher CHL was observed in BS,about 60%higher than that in GS.Compared with the northern regions of BS and GS(BSN and GSN),CHL in the southern region of BS and GS(BSS and GSS)increased by 77%and 42%respectively.More ice melting in BSN is the main reason for phytoplankton proliferation.In 2010,there was an unusual peak of CHL concentration in GSN.The sea-sonal peaks of CHL appeared two weeks earlier in BS than in GS.The earlier and more extensive ice melting and the persistent nega-tive North Atlantic Oscillation(NAO)index may be the reasons for higher CHL blooms in 2010.The spatial average ICE concentra-tion of BS in BSN and BSS is 27%and 1.2%respectively.Negative NAO in the previous winter may lead to an increase in ICE in spring.NAO has a great influence on CHL and ICE in GS.Ice melting is positively correlated with CHL,especially in GS in recent decades,CHL has a significant positive correlation with surface mass concentration of dimethylsulfide(DMS),especially in GS.As an indicator of Arctic warming,BS needs more attention from Arctic researchers.

Effects of multiple dynamic processes on chlorophyll variation in the Luzon Strait in summer 2019 based on glider observation

Luzon Strait is the main channel connecting the South China Sea(SCS)and the western Pacific,with complex atmospheric and oceanic dynamic processes.Based on 44 days of glider measurements and satellite observations,we investigated the temporal and vertical variations of chlorophyll-a(Chl-a)concentration in the Luzon Strait from July 25 to September 6,2019.The Chl a was mainly distributed above 200 m and concentrated in the subsurface chlorophyll maximum(SCM)layer.The depth of SCM ranged between 50 m and 110 m,and the magnitude of SCM varied from 0.42 mg/m3 to 1.12 mg/m3.The variation of Chl a was identified with three stages responding to different dynamic processes.Under the influence of Kuroshio intrusion,the SCM depth sharply deepened,and its magnitude decreased in Stage 1.Afterward,a prominent Chl-a bloom was observed in the SCM layer from August 6 to August 16.The Chl-a bloom in Stage 2 was related to the influence of a cyclonic eddy,which uplifted of the thermocline and thus the deep nutrients.During Stage 3,prolonged heavy rainfall in the northeastern SCS resulted in a significant salinity decrease in the upper ocean.The convergence of upper water deepened the thermocline and the mixed layer.Thus,the Chl a decreased in the SCM layer but increased in the surface layer.In particular,a typhoon passed through the Luzon Strait on August 24,which induced the Chl a increase in the upper 50 m.However,there was little change in the depth-integrated Chl a(0-200 m),indicating that the Chl a increase in the surface layer was likely associated with physical entrainment of SCM caused by strong mixing,rather than the phytoplankton bloom in the upper water column.Underwater gliders provide frequent autonomous observations that help us understand the regional ocean’s complex dynamic processes and biological responses.

Effects of drought treatment on photosystemⅡactivity in the ephemeral plant Erodium oxyrhinchum

Drought is a critical limiting factor affecting the growth and development of plants in arid and semi-arid areas.Photosynthesis,one of the most important physiological processes of plants,can be significantly inhibited by drought.PhotosystemⅡ(PSⅡ)is considered the main attack target when photosynthesis is affected by drought.To clarify how PSⅡcomponents of the ephemeral plant Erodium oxyrhinchum(grown in the Gurbantunggut Desert,China)respond to drought treatment,we evaluated the functional activity of PSII by determining chlorophyll fluorescence and gas exchange parameters under different drought treatment levels(control(400 mL),moderate drought(200 mL),and severe drought(100 m L)).Under moderate drought treatment,significant decreases were found in net photosynthetic rate(Pn),effective quantum yield of PSII(Y(Ⅱ)),relative electron transfer rate of PSII(rETR(Ⅱ)),oxygen-releasing complex,probability of an absorbed exciton moving an electron into the electron transport chain beyond primary quinone receptor Q_(A)-(Φ(E_(o))),probability of a trapped exciton moving an electron into the electron transport chain beyond primary quinone receptor Q_(A)-(ψ(E_(o))),and performance index of PSⅡ(PI_(abs)).Compared to control treatment,marked increases were observed in water use efficiency(WUE),relative variable fluorescence at the J step(V_(J)),initial fluorescence(F_(o)),and dissipated energy per active reaction center(DI_(o)/RC)under moderate drought treatment,but there were no substantial changes in semi-saturated light intensity(I_(K)),active reaction centers per cross-section(RC/CS),and total performance index of PSII and PSI(PI_(total),where PSI is the photosystemⅠ).The changes of the above parameters under severe drought treatment were more significant than those under moderate drought treatment.In addition,severe drought treatment significantly increased the absorbed energy per active reaction center(ABS/RC)and trapping energy per active reaction center(TR_(o)/RC)but decreased the energy transmission connectivity of PSⅡcomponents,RC/CS,and PI_(total),compared to moderate drought and control treatments.Principle component analysis(PCA)revealed similar information according to the grouping of parameters.Moderate drought treatment was obviously characterized by RC/CS parameter,and the values of F_(o),V_(J),ABS/RC,DI_(o)/RC,and TR_(o)/RC showed specific reactions to severe drought treatment.These results demonstrated that moderate drought treatment reduced the photochemical activity of PSII to a certain extent but E.oxyrhinchum still showed strong adaptation against drought treatment,while severe drought treatment seriously damaged the structure of PSⅡ.The results of this study are useful for further understanding the adaptations of ephemeral plants to different water conditions and can provide a reference for the selection of relevant parameters for photosynthesis measurements of large samples in the field.

Irrigation mitigates the heat impacts on photosynthesis during grain filling in maize

Elevating soil water content(SWC)through irrigation was one of the simple mitigation measures to improve crop resilience to heat stress.The response of leaf function,such as photosynthetic capacity based on chlorophyll fluorescence during the mitigation,has received limited attention,especially in field conditions.A two-year field experiment with three treatments(control treatment(CK),high-temperature treatment(H),and high-temperature together with elevating SWC treatment(HW))was carried out during grain filling with two maize hybrids at a typical station in North China Plain.Averagely,the net photosynthetic rate(Pn)was improved by 20%,and the canopy temperature decreased by 1–3℃ in HW compared with in H in both years.Furthermore,the higher SWC in HW significantly improved the actual photosynthetic rate(Phi2),linear electron flow(LEF),variable fluorescence(F_(v)),and the maximal potential quantum efficiency(F_(v)/F_(m))for both hybrids.Meanwhile,different responses in chlorophyll fluorescence between hybrids were also observed.The higher SWC in HW significantly improved thylakoid proton conductivity(g H^(+))and the maximal fluorescence(F_(m))for the hybrid ZD958.For the hybrid XY335,the proton conductivity of chloroplast ATP synthase(v H^(+))and the minimal fluorescence(Fo)was increased by the SWC.The structural equation model(SEM)further showed that SWC had significantly positive relationships with Pn,LEF,and F_(v)/F_(m).The elevating SWC alleviated heat stress with the delayed leaf senescence to prolong the effective period of photosynthesis and enhanced leaf photosynthetic capacity by improving Phi2,LEF,Fv,and F_(v)/F_(m).This research demonstrates that elevating SWC through enhancing leaf photosynthesis during grain filling would be an important mitigation strategy for adapting to the warming climate in maize production.

Testing phaeophytinization as an index of ozone stress in trees

Ground-level ozone pollution is a menace for vegetation in the northern hemisphere,limiting photosynthetic pigments and suppressing photosynthesis in trees and other types of plants.Phaeophytinization is the process of converting chlorophylls into phaeophytins,for example by acidifi cation.Ozone is a highly oxidizing molecule and well known to degrade chlorophylls;however,the eff ect of ozone on phaeophytinization in leaves of higher plants is largely unknown.To reveal ozone eff ect on phaeophytinization and evaluate the potential of phaeophytinization as an index of ozone stress in trees,the absorbance at the optical density of 665 nm was measured before(OD_(665))and after(OD_(665a))acidifi cation in three independent experiments with nearly 30 conditions of ozone exposure.Both current ambient and elevated ozone widely aff ected phaeophytinization,as indicated by decreases or increases in the phaeophytinization quotient OD_(665)/OD_(665a).These eff ects were commonly moderate to large in magnitude and practically signifi cant,and occurred even in ozone-asymptomatic leaves.It emerges that the ozone eff ect on phaeophytinization is bimodal,likely depending on the intensity of ozone stress.These results indicate a promising feature of OD_(665)/OD_(665a)as a thorough index of ozone stress in the future,but further studies are needed to reveal the underlying biochemical mechanisms of the bimodal eff ect on phaeophytinization.

Variations in chlorophyll content, stomatal conductance, and photosynthesis in Setaria EMS mutants

Chlorophyll (Chl) content,especially Chl b content,and stomatal conductance (G_s) are the key factors affecting the net photosynthetic rate (P_n).Setaria italica,a diploid C_4 panicoid species with a simple genome and high transformation efficiency,has been widely accepted as a model in photosynthesis and drought-tolerance research.The current study characterized Chl content,G_s,and P_n of 48 Setaria mutants induced by ethyl methanesulfonate.A total of 24,34,and 35 mutants had significant variations in Chl content,G_s,and P_n,respectively.Correlation analysis showed a positive correlation between increased G_s and increased P_n,and a weak correlation between decreased Chl b content and decreased P_n was also found.Remarkably,two mutants behaved with significantly decreased Chl b content but increased P_n compared to Yugu 1.Seven mutants behaved with significantly decreased G_s but did not decrease P_(n )compared to Yugu 1.The current study thus identified various genetic lines,further exploration of which would be beneficial to elucidate the relationship between Chl content,G_s,and P_n and the mechanism underlying why C_4 species are efficient at photosynthesis and water saving.

Epipelagic mesozooplankton communities in the northeastern Indian Ocean off Myanmar during the winter monsoon

The northern Andaman Sea off Myanmar is one of the relatively high productive regions in the Indian Ocean.The abundance,biomass and species composition of mesozooplankton and their relationships with environmental variables in the epipelagic zone(~200 m)were studied for the first time during the Sino-Myanmar joint cruise(February 2020).The mean abundance and biomass of mesozooplankton were(1916.7±1192.9)ind./m3and(17.8±7.9)mg/m3,respectively.A total of 213 species(taxa)were identified from all samples.The omnivorous Cyclopoida Oncaea venusta and Oithona spp.were the top two dominant taxa.Three mesozooplankton communities were determined via cluster analysis:the open ocean in the Andaman Sea and the Bay of Bengal(Group A),the transition zone across the Preparis Channel(Group B),and nearshore water off the Ayeyarwady Delta and along the Tanintharyi Coast(Group C).Variation partitioning analysis revealed that the interaction of physical and biological factors explained 98.8%of mesozooplankton community spatial variation,and redundancy analysis revealed that column mean chlorophyll a concentration(CMCHLA)was the most important explanatory variable(43.1%).The abundance and biomass were significantly higher in Group C,the same as CMCHLA and column mean temperature(CMT)and in contrast to salinity,and CMT was the dominant factor.Significant taxon spatial variations were controlled by CMCHLA,salinity and temperature.This study suggested that mesozooplankton spatial variation was mainly regulated by physical processes through their effects on CMCHLA.The physical processes were simultaneously affected by heat loss differences,freshwater influx,eddies and depth.

Epigenetic modification mechanisms of chloroplasts mutants in pineapple leaves during somatic regeneration

Somaclonal variation in tissue culture is a common phenomenon induced by various external or internal environmental conditions,resulting in heritable or non-heritable alterations in gene expression. One crucial mechanism involved in plant growth and development is epigenetic regulation. A highly dynamic epigenome can respond to environmental changes by regulating gene expression. DNA methylation is one of these epigenetic modifications that can alter gene expression in tissue-cultured pineapple plants. The underlying mechanism of such somaclonal variations in pineapple and the epigenetic regulation involvement in somaclonal variations has not been studied. This study performed DNA methylome and transcriptome sequencing of wild-type(WT) and mutant pineapple plants(WS, HW, and TW). We observed altered DNA methylation patterns in chlorophyll development in the mutants. Specifically, we noticed that the methylation levels in the CHG and CHH contexts were lower in the gene body regions compared to the upstream and downstream regions. We identified several thousand differentially methylated regions(DMRs) located at the gene body regions, some of which overlapped with the differentially expressed genes(DEGs). Functional enrichment analyses suggested that these genes were involved in chlorophyll metabolism. Thus, our results revealed that the transcriptional regulation of many chlorophyll metabolic essential genes could be regulated by DNA methylation caused by somaclonal variations and provided insights into epigenetic mechanisms underlying the regulation of chlorosis in pineapple plants.

Impact of ZnSO_(4)^(-)and ZnO Nanoparticles on Seed Germination and Seedling Growth of Lettuce

Micronutrient nanoparticles(NPs)are currently an option for chemical fertilization and biostimulation in crops.However,there is little information on the phytotoxic or biostimulatory effects of NPs at low concentrations of some elements,such as Zn.In this study,the effect of low concentrations of Zn oxide(ZnO)NPs on germination,growth variables,and nutritional attributes of lettuce(Lactuca sativa L.)was evaluated in comparison to Zn sulfate.Romaine lettuce seeds were treated with ZnSO_(4)^(-)×7H_(2)O and ZnO NPs at Zn molar concentrations of 1×10^(−3),5×10^(−3),1×10^(−4),5×10^(−4),1×10^(−5),5×10^(−5),1×10^(−6),and 5×10^(−6).The seeds treated with ZnSO4−at 5×10^(−6)registered the highest radicle length,73%more than the control treatment.The seeds treated with ZnSO4−at 5×10^(−3)registered the lowest values,with 50%less than the control treatment.ZnO NPs at 5×10^(−6)significantly increased content of chlorophyll A and B and total phenolics.These results indicate the possible existence of a mechanism related to the intrinsic nanoparticle properties,especially at low concentrations.

Evaluation of Pre-Emergence and Post-Emergence Herbicides for Weed Management in Miscanthus sacchariflorus and Miscanthus sinensis

Miscanthus,is a promising bioenergy crop,considered superior to other bioenergy crops because of its higher water and nutrient use efficiency,cold tolerance,and higher production of biomass.Broadleaf weeds and grass weeds,cause major problems in the Miscanthus field.A field experiment was conducted in 2018 and 2019,to assess the effects of pre-emergence(alachlor and napropamide)and post-emergence herbicides(nicosulfuron,dicamba,bentazon,and glufosinate ammonium)on broadleaf and grass weeds in M.sinensis and M.sacchariflorus fields.The weed control efficiency and phytotoxicity of pre-and post-emergence herbicides were evaluated at 30 days after treatment(DAT)and compared to those of the control plots.The results showed wide variations in the susceptibility of the weed species to the treated herbicides.Treatment with nicosulfuron 40 g.a.i.ha^(-1) provided the most effective overall weed control(with 10%visual injury),without affecting the height and biomass of neither Miscanthus species in the field.Post-emergence herbicides such as glufosinate ammonium 400 g.a.i.ha^(-1) and dicamba 482 g.a.i.ha^(-1) were effective and inhibited the growth and density of the majority of weeds to a 100%;however,they showed significant phytotoxicity(toxicity scale of 1-10)to both species of Miscanthus.The application of glufosinate ammonium caused severe injuries to the foliar region(90%visual injury)of both Miscanthus sps.Comparatively,M.sinensis showed a slightly higher tolerance to the herbicides nicosulfuron,bentazon and napropamide with 10%visual injury at the recommended dose than M.sacchariflorus.The present study clearly showed that infestation of broadleaf and grass weeds in Miscanthus fields can cause significant damage to the growth and biomass of Miscanthus and applying pre-emergence and post-emergence herbicides effectively controls the high infestation of these weeds.

Seasonal variation of the shape and location of the Luzon cold eddy

Using observational data from multiple satellites,we studied seasonal variations of the shape and location of the Luzon cold eddy(LCE)northwest of Luzon Island.The shape and location of the LCE have obvious seasonal variations.The LCE occurs,develops,and disappears from December to April of the next year.During this period,the shape of the LCE changed from a flat ellipse to a circular ellipse,and the change in shape can be reflected by the increase of the ellipticity of the LCE from 0.16 to 0.82.The latitude of center location of the LCE changes from 17.4°N to 19°N,and the change in latitude can reach 1.6°.Further study showed that seasonal variation of the northeast monsoon intensity leads to the change in the shape and location of the LCE.The seasonal variation of the LCE shape can significantly alter the spatial distribution of the thermal front and chlorophyll a northwest of the Luzon Island by geostrophic advection.

Natural variations and geographical distributions of seed carotenoids and chlorophylls in 1167 Chinese soybean accessions

Understanding the composition and contents of carotenoids in various soybean seed accessions is important for their nutritional assessment.This study investigated the variability in the concentrations of carotenoids and chlorophylls and revealed their associations with other nutritional quality traits in a genetically diverse set of Chinese soybean accessions comprised of cultivars and landraces.Genotype,planting year,accession type,seed cotyledon color,and ecoregion of origin significantly influenced the accumulation of carotenoids and chlorophylls.The mean total carotenoid content was in the range of 8.15–14.72μg g–1 across the ecoregions.The total carotenoid content was 1.2-fold higher in the landraces than in the cultivars.Soybeans with green cotyledons had higher contents of carotenoids and chlorophylls than those with yellow cotyledons.Remarkably,lutein was the most abundant carotenoid in all the germplasms,ranging from 1.35–37.44μg g–1.Carotenoids and chlorophylls showed significant correlations with other quality traits,which will help to set breeding strategies for enhancing soybean carotenoids without affecting the other components.Collectively,our results demonstrate that carotenoids are adequately accumulated in soybean seeds,however,they are strongly influenced by genetic factors,accession type,and germplasm origin.We identified novel germplasms with the highest total carotenoid contents across the various ecoregions of China that could serve as the genetic materials for soybean carotenoid breeding programs,and thereby as the raw materials for food sectors,pharmaceuticals,and the cosmetic industry.

Drought Tolerance in Mung Bean is Associated with the Genotypic Divergence, Regulation of Proline, Photosynthetic Pigment and Water Relation

Drought is one of the critical conditions for the growth and productivity of many crops including mung bean(Vigna radiata L.Wilczek).Screening of genotypes for variations is one of the suitable strategies for evaluating crop adaptability and global food security.In this context,the study investigated the physiological and biochemical responses of four drought tolerant(BARI Mung-8,BMX-08010-2,BMX-010015,BMX-08009-7),and four drought sensitive(BARI Mung-1,BARI Mung-3,BU Mung-4,BMX-05001)mung bean genotypes under wellwatered(WW)and water deficit(WD)conditions.The WW treatment maintained sufficient soil moisture(22%±0.5%,i.e.,30%deficit of available water)by regularly supplying water.Whereas,the WD treatment was maintained throughout the growing period,and water was applied when the wilting symptom appeared.The drought tolerant(DT)genotypes BARI Mung-8,BMX-08010-2,BMX-010015,BMX-08009-7 showed a high level of proline accumulation(2.52–5.99 mg g^(−1) FW),photosynthetic pigment(total chlorophyll 2.96–3.27 mg g^(−1) FW at flowering stage,and 1.62–2.38 mg g^(−1) FW at pod developing stage),plant water relation attributes including relative water content(RWC)(82%–84%),water retention capacity(WRC)(12–14)as well as lower water saturation deficit(WSD)(19%–23%),and water uptake capacity(WUC)(2.58–2.89)under WD condition,which provided consequently higher relative seed yield.These indicate that the tolerant genotypes gained better physiobiochemical attributes and adaptability in response to drought conditions.Furthermore,the genotype BMX-08010-2 showed superiority in terms of those physio-biochemical traits,susceptibility index(SSI)and stress tolerance index(STI)to other genotypes.Based on the physiological and biochemical responses,the BMX-08010-2 was found to be a suitable genotype for sustaining yield under drought stress,and subsequently,it could be recommended for crop improvement through hybridization programs.In addition,the identified traits can be used as markers to identify tolerant genotypes for drought-prone areas.